The present invention relates generally to a hydraulic control circuit having a variable feedback path and more particularly to a hydraulic control circuit for the steering system of an articulated vehicle to provide variable steering for that vehicle.
It is well known that certain articulated vehicles utilized in construction, mining, and logging require relatively fast or responsive steering for certain operations and require relatively slow or unresponsive steering at other times. For example, logskidders require fast steering on the job to enable the vehicle to "duck walk" or assist the tractive effort of the skidder to pull it out of axle-deep mud. On the road, however, where the vehicle may be operated at higher travel speeds, fast or responsive steering can be dangerous, and therefore is undesirable. Thus, for road travel, it is desirable to have slow or relatively unresponsive steering. This problem has been solved heretofore by the use of complex mechanical linkages to provide multi-rate steering; by the use of plural pump systems; by the use of an accumulator to back up the normal pump pressure for increased responsiveness; and by the use of flow divider valves to vary steering rates. All of these systems have been relatively complex in nature.